1. Field of the Invention
The present invention relates to a liquid discharging head that discharges a liquid, such as ink, and to a method for producing the same.
2. Description of the Related Art
Hitherto, a liquid discharging head that is used in a liquid discharging device and that includes a recording element substrate, a supporting member to which the recording element substrate is bonded, and an electric wiring substrate provided with lead terminals that are connected to connection terminals at the recording element substrate has been available. In order to prevent faulty connection, such as wire breakage, caused by outside force or corrosion by a liquid, connecting portions between the connection terminals of the recording element substrate and the lead terminals of the electric wiring substrate are covered and sealed with a sealing material after connecting each substrate to the supporting member with an adhesive. As a method for sealing the connecting portions, a method for applying a sealing material to a top portion of each lead terminal and causing the sealing material to enter from portions between the lead terminals that are adjacent to each other, to fill the portions between the lead terminals that are adjacent to each other up to lower portions of the lead terminals is known. However, in this sealing method, it is difficult to fill spaces at the lower portions of the lead terminals with the sealing material in one applying operation. This may cause improper sealing at the lower portions of the lead terminals due to, for example, cavities and air bubbles.
As a measure against such improper sealing, Japanese Patent Laid-Open No. 2002-079675 (Japanese Patent Laid-Open No. 2002-079675) discloses a structure in which a sealing material receiver is provided at the lower portions of the lead terminals. In this structure, the sealing material receiver receives the sealing material moving towards the lower portions of the lead terminals from gaps between the plurality of lead terminals that are adjacent to each other. This increases the coverability by the sealing material near the lead terminals. Therefore, it is possible to reduce improper sealing and to prevent faulty connection occurring when the lead terminals are corroded by ink.
According to the technology discussed in Japanese Patent Laid-Open No. 2002-079675, faulty connection caused by corrosion of the lead terminals by ink is prevented by increasing the coverability of the vicinity of the lead terminals by the sealing material. However, in this technology, corrosion of the lead terminals caused by contact with an adhesive when, before sealing the lead terminals with the sealing material, the electric wiring substrate provided with the lead terminals is bonded to the supporting member with the adhesive is not considered. In order to firmly bond the electric wiring substrate to the supporting member with the adhesive, it is necessary to apply the adhesive to a certain thickness. In particular, when the supporting member is formed of a resin material and has a low flatness accuracy, it is necessary to apply the adhesive to a greater thickness. In this case, the adhesive that has been pressed down to the electric wiring substrate during the bonding step may protrude from the supporting member and contact the lead terminals.
In general, as an adhesive for bonding the supporting member and the electric wiring substrate to each other, a photo-curable adhesive whose principal component is epoxy resin and that is electrically conductive is used. Therefore, when the adhesive protruding from the supporting member contacts the lead terminals, the lead terminals are electrically connected with each other through the adhesive, as a result of which the lead wires may become corroded. Therefore, instead of using a photo-curable adhesive, a thermosetting adhesive having a volume resistivity that is higher than that of a photo-curable adhesive may be used. However, the bond strength of a thermosetting adhesive is lower than that of a photo-curable adhesive. Therefore, when a thermosetting adhesive is used, the electric wiring substrate and the supporting member may not be sufficiently bonded to each other.